1. Technical Field
The present invention relates to a cryptographic communication apparatus and a cryptographic communication system which conduct a key exchange procedure and an authentication procedure, and more particularly to a cryptographic communication apparatus and a cryptographic communication system, which conduct an SSL (secure socket layer) cryptographic communication and a password mutual-authentication protocol such as a password authenticated key exchange (hereinafter referred to as “PAKE authentication”).
2. Description of the Related Art
In recent years, as secure communication methods, an SSL/TLS cryptographic communication has been popularized. The SSL/TLS cryptographic communication is very simply available, protected against the most dangerous man-in-the-middle attack in the cryptographic communication, and very high in security.
However, coping with the man-in-the-middle attack requires a mechanism of a PKI (public key infrastructure) used in a Server Certificate and a client certificate, and therefore is complicated in operation and increased in maintenance costs as compared with usual password authentication.
In recent years, as means for compensating the above drawbacks, the PAKE authentication has been increasingly studied. The PAKE authentication is a new authentication system which combines a public key cryptosystem and the password authentication together, differently from the conventional password authentication. With the use of the PAKE authentication, the inexpensive and simple password can be used to suppress the man-in-the-middle attack instead of the expensive and complicated PKI.
However, even if it is theoretically possible to realize the cryptographic communication and the authentication at the same time by only the PAKE authentication, actual operation is remarkably difficult. For that reason, there has been proposed a technique by which various communication devices such as firewalls and tools such as browser accept the SSL/TLS cryptographic communication, and conduct the PAKE authentication by using the mechanism of the widespread SSL/TLS cryptographic communication without any change. A client and a server conduct SSL/TLS negotiation (SSL/TLS handshake), and thereafter conduct the PAKE authentication, to thereby suppressing damage from the man-in-the-middle attack (refer to JP-A-2009-296190).